Yes, this is quite a silly question considering I've been gamemastering for almost five years now, but one thing that drove me away from (and the same thing that made me return to) D&D 4E was Dungeon Crawling.

We've been using Savage Worlds as our system for a while, but we finally decided to give 4E a second go since we really like the encounters.

Since my group is comprised by two local friends and two foreigners, we use Roll20.net to play our adventures. However I don't have any idea on how to run an actual dungeon crawl using a virtual tabletop.

What I've tried is saving the map image as a file and then using it on the virtual tabletop and using fog of war for vision, however this has two issues:

Playing becomes very boring since it's a mess to constantly move the character minis on the map every time they wish to check something and I constantly have to fiddle with the Fog of War. Some rooms that only have loot feel like a hindrance instead of a reward as we have to laboriously move minis through them while I remove the fog.

The whole map feels like just one big encounter map if we "walk" through it. Instead of specific areas being unique encounters (like "the Torture Chamber is plagued by ghosts" or "this Slime Pit is the home of a Solo Monster") my players start leading the monster into other parts of the map, sometimes making the long encounter way longer. The rooms for encounters lose their focus, and the preparation feels wasted since, well, I designed them for the encounter.

Since the encounters are what brought us back to D&D 4e and dungeoncrawls, these things are really undermining the enjoyment we were hoping for.

So, how do you actually navigate players through a dungeon in an online game?

5 Answers
5

Usually I either describe the dungeon verbally, only drawing out the rooms that the players interact with, or I draw the overview of the map on another sheet of paper. I think the problems you're having are a symptom of using an online table.

Here are some ideas.

Do the dungeon verbally .. err... textually. Describe rooms to the players. Load them up as needed.

Don't put treasure and monsters on the map in advance. Add them when the players go into the right room. That should help with some of the Fog of War tedium.

Treat the party as a single entity. Instead of moving the fighter, then the rogue, then the wizard, then the cleric, just move the party token. When an encounter happens, determine more specific positions.

I'd also like to respond to this part:

my players start leading the monster into other parts of the map,
sometimes making the long encounter way longer. The rooms for
encounters lose their focus, and the preparation feels wasted since,
well, I designed them for the encounter.

That's okay! You're not running a video game. You're running a pen and paper roleplaying game, albeit facilitated by an electronic table simulator. One of the strengths of P&P RPGs is that the players can go anywhere and do anything that the GM can react to instead of being cut off by what the designer/programmer planned for. The fact that the players wander into another room that you thought would be offscreen is fine. It means the players have choice and can act on that choice, even if it makes their battleground a little less interesting.

I found this aspect of Roll20 is nice if you have the time to set it up correctly, but I didn't find it added a lot of value for my players. I've taken the approach of drawing my map out as we go, without using Fog of War. That way I only have to add the details that are necessary as we go, rather than drawing out every detail and risk some of it never being seen at all. In short, if it's not adding value to your game, stop using it.

Setting up interesting room-based encounters:

If your party is luring the big bad away from his fancy chamber, give him a reason to remain fixed there. An adventure I ran had a living shadow that could only persist in the room he appears, as there was a burned out, evil firepit that was the source of it's projection, making it fairly impossible to leave. If the party tried to bait it, it simply hid in the room out of view, leaving the party unsure where it was upon return. A demonic encounter could have a series of wards that prevents the creatures from leaving beyond a certain distance. An outsider creature could have a source of energy it couldn't stray far from, or perhaps a series of sources that it has to stay near. In addition to that, whose to say there aren't monsters that are aware of the party coming and would be prepared for their intrusion? Keep in mind the intelligence values of the creatures they are up against and what is in the dungeon to help them defend themselves. A clever monster may be aware of where the party is trying to lure them and come up with an alternate plan or call for help. Smarter foes will also have an exit strategy if things don't go their way.

It's also worth noting that not stopping between encounters, or causing them to mix together, is a valid PC strategy sometimes (though only sometimes), especially since not stopping for a rest before hitting another encounter earns Action Points.
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SevenSidedDie♦Jun 17 '14 at 21:31

Remember, you can make each room its own map.
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GMNoobJun 18 '14 at 15:31

The whole map feels like just one big encounter map if we "walk" through
it. Instead of specific areas being unique encounters (like "the
Torture Chamber is plagued by ghosts" or "this Slime Pit is the home
of a Solo Monster") my players start leading the monster into other
parts of the map, sometimes making the long encounter way longer. The
rooms for encounters lose their focus, and the preparation feels
wasted since, well, I designed them for the encounter.

Right there, you have an obvious problem: you are designing monsters that are too static, and you haven't got a reason for them to be static, so your players make them move. Your players are taking advantage of what they see before them, using tactics and movement to fight better. So, what's your reason for the ghosts to be in the room? Why is the slime lord confined to the pit?

Ideally, there's something for the players to get in those rooms (loot, information, people), and they have to go there. Ideally, the monsters are stuck there, half mad, unable to get out. Perhaps the ghosts haunt that room. Perhaps they can't actually perceive the exit because of a curse. Perhaps you can lock the door after people enter (a la Legend of Zelda). Or, perhaps, you can account for the perfectly reasonable possibility that your adventurers and monsters actually move. You'll get a living dungeon.

This has the corollary that walking around the dungeon shouldn't be "free". The main part of the adventure "Cairn of the Winter King" (included in the Monster Vault for 4E Essentials) is an example of a dungeon with tips for what to do if the players escape an encounter, or make too much noise. Random patrols are described, and it suggests adding monsters to an encounter because the characters weren't stealthy enough.

Playing becomes very boring since it's a mess to constantly move the character minis on the map every time they wish to check something and I constantly have to fiddle with the Fog of War. Some rooms that only have loot feel like a hindrance instead of a reward as we have to laboriously move minis through them while I remove the fog.

The Fog of War feature in Roll20 is very much a sledgehammer, so I don't recommend using it as a scalpel. While as a player it might be cool to see the dungeon revealed before me as I progress, this puts a lot of effort on the GM to keep up with the players' movement with the FoW Reveal tool, and switching between that and the select tool for moving the monsters, and maybe even the drawing tool to indicate Zone, Blasts, and Bursts.

Instead, consider letting everything be revealed from the start except for areas you specifically don't want the players to see yet. True, it's not quite the same experience for the player, but it's much less work at game time for you. You can still leave rooms hidden behind secret doors, plot-important areas can still be shrouded in darkness, etc. until you're ready for the players to go there, but at least you don't have to play babysitter with the fog layer.

That said you may find it worth your while to invest in a subscription. Supporter-level ($5/mo or $50/yr) gives you access to the Dynamic Lightning feature. With DL, you set up light-blocking walls using the drawing tool, and set the players' tokens to emit light. As the player moves around, they get to see the nearby portions of the map automatically, without you having to babysit the fog layer. You can also use the Dynamic Lighting walls to block movement: players will not be able to drag their token through a DL wall.

Then again, the cost of the subscription might not be worth it to you.

The whole map feels like just one big encounter map if we "walk" through it. Instead of specific areas being unique encounters (like "the Torture Chamber is plagued by ghosts" or "this Slime Pit is the home of a Solo Monster") my players start leading the monster into other parts of the map, sometimes making the long encounter way longer. The rooms for encounters lose their focus, and the preparation feels wasted since, well, I designed them for the encounter.

This is a problem with the encounter/dungeon design, not with the Virtual Tabletop. If you have the encounter set up such that the players can drag the monster all over the dungeon (and especially if it is advantageous for them to do so), then they could do it whether you're on Roll20, MapTool, Fantasy Grounds, or all gathered in your living room.

If you want to prevent this from happening, you need to have a reason for it to not happen. The two general strategies for this are to either prevent the players from leaving the room (eg, lock the door behind them when they enter), or prevent the monster from following them out of the designated encounter area.

You shouldn't have to do anything to adjust vision if you are using a robust virtual tabletop like maptool. It will automatically reveal vision to players based on what their token can see (based on its type of vision and the type of light, if any, that is available). Any VTT that makes you adjust fog is not worth using.

Why do your monsters follow the PCs out of their lairs? And have you considered using wandering monsters?

So, just to be clear, your answers is "Don't use Roll20"? Also be aware that asking a question in your answer doesn't work: this isn't a forum, the OP has no way of answering your questions. If that doesn't make any sense, consider taking our tour and seeing how our Q&A site is different from a forum and requires a different kind of post.
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SevenSidedDie♦Sep 12 '14 at 18:11

Roll20 does have dynamic lighting, it's simply a subscription feature. R20's dynamic lighting even allows for things like shaped light sources (eg, hooded lanterns) and walls blocking vision of other light sources (eg, you can't see the fire until you round the corner).
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Brian SSep 12 '14 at 19:01